Abstract:

Promoting interfacial reaction kinetics is highly desirable for achieving high-performances of anode material in alkali-ion batteries. Herein, flower-like MoSe₂/MoO_3-x@rGO composites are fabricated by a facile solvothermal method involving a thermal-treatment at 800°C. When evaluated as an anode material for potassium ion batteries, MoSe₂/MoO_3-x@rGO delivers 248.2 mA h g^-1 after 50 cycles at 0.2 A g^-1 with a capacity retention of 84.6% and 182.9 mA h g^-1 after 150 cycles at 1.0 A g^-1 with a capacity retention of almost 61.2%, superior to those of bare MoSe₂ or MoSe₂@rGO composites. Analysis from electrochemical measurements, the amorphous MoO_3-x containing oxygen vacancies could not only effectively buffer the self-aggregation of MoSe₂ nanosheets but also provides lots of accessible active sites for potassium ion storage. Additionally, the open channels in the amorphous MoO_3-x phase lead to easier ion hopping and smaller diffusion barriers. Furthermore, the built-in electric field at the interface would be beneficial for electron transfer and K-ion migration across the hetero-junction interface. Moreover, larger dielectric polarization induced by the high relative permittivity of amorphous MoO_3-x would reduce charge transfer resistance and enhance K-ion migration across electric double-layer. Our work provides new insight into the enhanced performance of anode material coated by an amorphous layer with large relative permittivity.

Key words: Potassium ion batteries, MoSe₂, Amorphous, Work function, Heterojunction interface